Yes, 4 Nylon wheels ridding on an aluminium bar tends to be a recipe for vibration and any dirt on the bar is a bump in the road so more vibration... I notice more expensive units use a 2-bar and bushing system much like the Y axis has onlu it is a single bar or they use much higher quality rollers. I purchased a spare set of rollers so I may try them. And and then look around for something I can retro-fit that will give a smooth fast X Asis.